GTA
Airguns by Make and Model => Vintage Air Gun Gate => Topic started by: TerryM on January 08, 2017, 01:32:16 PM
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I have a kit I ordered for a 342, wondering if it will work in a 312 I picked up a couple of weeks ago.
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They're one and the same.
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Thanks, Scott. I tore down my 312 and replaced the seals while the Packers whupped the Giants this evening.
The 312 exhaust valve is a bugger. Has a single port that has to line up perfectly with the transfer port. I don't know how anyone does it. I happened to have a 342 parts gun in the closet so I pulled the exhaust valve out of it. It has the channel around the circumference and two ports, so it doesn't have to line up with anything. Worked fine. The valve nut is still nerve-wracking for me. This is only the second Benjamin I have resealed. This one seems to pump up fine and shoot hard, I'll be interested to see how it performs when it's nice enough outside to shoot over the chrony.
I like the way the 312 is put together at the front end, no roll pins. Easier to deal with, wish they'd have kept that feature.
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I'll second that with the lack of roll pins on the 31x's. I haven't done a single ported one in awhile. Wasn't there a brass notch so it could only go in with the port up? I can't recall. Be grateful it's not the one with the tapped/keyed lead washer. I do recall reading a thread where Tim commented that the single ported Benji's get higher FPS.
After you remove the guts. Take the valve nut and thread it on a couple of times without the internals. This will get everything cleaned up in the threads. Mark The Tool as well so you know where the thread catches.
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the 312 should have a tab, and corresponding notch in the valve. it will be on your right, as you look into the back of the valve. it would also have the lead washer, with the corresponding tab, as well.
they're really not that hard to assemble. it just takes patience.
I also agree with the no roll pin front ends. until you get one that the previous owner got a little carried away with tightening down the jam screw, and stripped the threads, that is.
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I did practice screwing and unscrewing the valve nut a few times without the insides in place. And I made a mark on the tool to show how far in it needed to be to engage the threads. Still... I have a hard enough time getting the nut started while working against the spring tension, without cross-threading... and to do this while trying to line up a tab on the valve (and washer) with a slot in the main valve body? Are you kidding?? I suppose it gets easier after you've done it a few times, it just looked like an impossible feat to me.
After I got the gun reassembled, lo and behold, what do I find on the table but my new lead washer! Seems to work fine without it, though. Held two pumps overnight, all is good. I even used the old pump cup since I didn't think I could get it off without destroying it and, since the piston is so easy to get to, I can replace it later if necessary. Might use the new cup in my 342.
Thanks for the responses, guys.
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the pump cup just pops off the end of the head. I use a small, dull screwdriver to pry them off. when putting the new one on, I find a little oil on the steel "pin" helps the cup seat easier.
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I guess you forgot the washer on valve nut? You might get a little blow by upon firing, but doubt it unless it starts to unscrew the nut. If down the road your POI starts to drop you'll know where to look. Glad you got her up and working though.
The cups for the 31x are much easier than the cups on everything else to remove and install.
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wild guess, but, I'd bet it's the front seal that he found. he probably didn't take the old lead seal out, to begin with. that's why it's not leaking. best advice, if it's working. LEAVE IT ALONE.
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The 312 was shooting a bit slow, it turned out. Put in a new pump cup and, today, took it back apart and reinstalled the original exhaust valve. Could not get a lead seal in behind it to save my life. Found there was one in front of it. Ended up putting everything back together without the rear lead seal. The gun shoots quite well, around 530 with six pumps and a JSB 13.4 gr. Eight pumps brings it up to 570 fps. Used a Sheridan intermount to attach an old Weaver B4. Hits the 1" bull every shot at 20 yards.
(http://i1076.photobucket.com/albums/w446/sotol11/IMG_1108%20-%20Copy_zpsnrf9vvia.jpg) (http://s1076.photobucket.com/user/sotol11/media/IMG_1108%20-%20Copy_zpsnrf9vvia.jpg.html)
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Well it's shooting and she looks good. That's all that counts. The valve nut may start coming unthreaded over time? Not sure, but at least you'll know where down the road if it does.
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I've found the lead seals a bit oversized. what I do is tap the back end of the valve tool, with a small ballpeen hammer to get the seal started past the threads. if you don't, you can't get the valve nut anywhere near the threads.